CD-sensitive Zn-porphyrin tweezer host-guest complexes, part 2: cis- and trans-3-hydroxy-4-aryl/alkyl-beta-lactams. A case study.

This article describes an application of the host-guest chiral recognition approach called tweezer methodology for the determination of the absolute configuration of 3-hydroxy-beta-lactams. These substrates represent challenging cases due to their chemical reactivity, the presence of multiple stereogenic centers and several functional groups which offer various possibilities of binding to the Zn-porphyrin host. OPLS-2005, the force field used in this work to predict the interporphyrin twist, modeled correctly the host-guest complexation mechanism and revealed conformational details of the bound substrates. The computational study also suggested that in cases where an increase in the magnitude of the stereodifferentiation and an intense experimental CD are observed, the bound conformation of the conjugates are hydrogen bonded. The present investigation provides evidence that when the tweezer method is assisted by the OPLS-2005 based computational approach, it can be successfully applied to the configurational and conformational elucidation of multi-functional compounds with multiple stereogenic centers.